Backfire oil trap for air cleaners



July 2, 1940 F. A. DONALDSON 2,206,718

BACKFIRE OIL TRAP FOR AIR CLEANERS Filed Jan. 16, 1959 Patented July 2, 1940 l UNITED STATES PATENT OFFiCE 2,206,718

BACKFIRE OIL TRAP FOR AIR. `CLEANERS Frank A. Donaldson, St. Paul, Minn. Application January 16, 1939, Serial No. 251,142

` 1 claim. (01. 18a-15) invention relates to air cleaners for use in connection with internal combustion' engines and of that type of air cleaner embodying a body of. fluid, usually oil, and more particularly the invention relates to a novel manner of forming backre oil traps in the intakes of such air cleaners.

`It isa well recognized fact that in air cleaners `of the type wherein a body of fluid such as oil is employed asa dust collecting medium, there is a tendency under occasional conditions of backring of the engine through its intake to blow the oil from the well out through the intake conduit or passage of the air cleaner. discharging of, oil by backfire very objectionable because it often results in reduced cleaning eiiiciency of the air cleaner, .due to the lowering of the oil level therein, but is further objectionable because such oil as is discharged under conditions of backfire is often blown over the surface of machinery, buildings and operators.

My present invention provides, at a minimum of cost and in a minimum of space, a highly cicient arrangement whereby dust collecting fluid displaced from the oil well and directed back-n wardly through the cleaner toward atmosphere, under instantaneous back pressure surges produced by backfiring of an engine, will be thrown out of the backwardly directed air stream in the air cleaners intake passage and will be trapped therein until the pressure surge occasioned by the backfire has passed, after which, the fluid is permitted to drain back by gravity into the well of the cleaner.` Although the present backiire l trap is applicable to various different types of uid containing air cleaners, it has been primarily designed for use in connection with air cleaners of the general character disclosed in'the patent to Lowther No. 2,069,889 of Feb. 9, 1937, and is herein illustrated in connection with an air cleaner of this general character.

The above and other important objects and advantages of the invention will be made apparent from the following specification, claim and drawing.

In the accompanying drawing, like characters indicate like parts throughout the several views.

Referring to the drawing:

Fig. 1 is a View in side elevation, with some parts broken away and shown in axial section, of an air cleaner incorporating the preferred form of the invention; i"

Fig. 2 is a transverse sectional the line 2-2 of Fig. 1; and

Not only is such view taken on Fig. 3 is a transverse sectional View taken on theline 3-3 of Fig. land looking upward.

The air cleaner illustrated includes a cylindrical shell or casing 4 that is primarily open at its lower end, but which is normally closed by an oil cup 5 that is telescopically applied thereto and removably held in placeby means including `wingnut equipped bolts 0. The head end of the cylindrical casing i is primarily closed by `a concave head member l. Opening axially through the concave head member 'I and leading downwardly into the oil well to a point below the static fluid` level therein `is an air intake conduit section 0. Surrounding the lower end` of the intake conduit section t and spaced both axially `and radially from the discharge end thereof and spaced radially from the sides of the oil well is an oil cup 9 having suitable metering openings 50a. Opening radially form the upper extreme portion of the casing 4 is an air outlet duct section l0 that is adapted to be connected to the air intake of an internal combustion engine in the conventional manner. Interposed in the annular space within the casing 4 surrounding the intake tube 8 and extending axially thereof between the vicinity of the'oil well and the vicinity of the air outlet l0,

is a suitable oil and dust intercepting means, which, in the particular form illustrated, is in the form of a series of corrugated annular screens Il of the nature disclosed and broadly claimed in the Schulz Patent No. 2,011,213 of August 13, 19,35. Applied over the screens Il is an air flow equalizing baffle plate l2 of the type disclosed and claimed in the Lowther Patent No. 2,006,927 of July 2,` 1935. l

The backfire oil trap, in its preferred form illustrated, is formed in part by the concave head member l and further includes a similar concave member la, which is applied to the head end of the air cleaner body in reverse relation with respect to the head member 7 so as to form an expansion chamber I3 of much greater diameter than the intake conduit section 8, and in which oil may be trapped. Opening downwardly into the expansion chamber f3 through the head member 'la is a primary intake conduitlsection i4, which latter conduit section is laterally or radially offset with respect to the axial conduit section 8 tosuch an extent that the interiors Ythereof are substantially out of axial alignment.

,In the arrangement just described, the conduit sections 8 and I4, which may be hereinafter referred to as small diameter sections, are axially spaced apart but are connected bythe large diameter intake section formed by the head members 'I and la. For the purpose of providing a suitable oil trapping baiile flange, the intake conduit section i4 is extended inwardly into the interior of the large diameter or expansion chamber I3 at Ma.

The intake sections 8 and I l open into the large diameter expansion chamber through suitable ports l5 and it, respectively. Due to the convexity or voutwardly bulging shape of the head section la and the fact that the intake section It is tangential with the peripheral portion of the head section la, the inner end Ita of the conduit It projects inward of the head section 'ISL to a maximum extent, at that circumferential portion thereof laterally most closely adjacent the conduit section 8. l

Operation When the apparatus described is coupled in the conventional manner to the intake of an internal combustion engine and the engine is operating normally, air will be drawn successively through the intake conduit sections I4, i3 and 8 and discharged downwardly against the body of oil in the oil Well within the oil cupr 9, and from thence will pass upwardly through the annular screen containing Vchamber' surrounding the intakey tube section 8 to'ancl through the air cleaners outlet section it to the engine. Under such normal operation, of; course, oil y will be carried with the air stream from the well into the screen chambei, but such oil as is lifted into the screen chamber will be intercepted by the screens during its passage therethrough and removed from the upwardly moving air stream before reaching the outlet It. Under such normal operation, the air passing downwardly through the enlarged diameterexpansion chamber I3 between the axially spaced ends of the radially offset intake sections I4 and 8 merely makes a gentle curve within the chamber i3, as indicated by full line airflow indicating arrows in Fig. 1, so that the oil trap arrangement produces a very minimum of restriction to air iiow in the intake.

When the engine backires, the backfireV explosion produces a momentary but quite high back pressure in the intake duct leading to the cleaners outlet Ii), as a result of which there is produced a rapid backward movement of air downwardly through the annular screen chamber. This downward movement of air, upon striking the oil in the well` surrounding the intake conduit 3, causes oil to be displaced from the oil cup S and blown with great rapidity up. wardly through the cleaners axial intake conduit section t with air that is directed to atmosphere. The air thus shot backwardly through the air cleaner to atmosphere, Vunder the instantaneous back pressure resulting from the backfire explosion, will follow the curved path indicated by full line arrows in Fig. l, but in reverse direction, between the upper end of the intake section 8 and the axially spaced radially offset inner end of the intake section i4, but the oil thus shot upwardly through the intake section 8, at high velocity, will centrifugate out of the air stream as it makes its curve between axially spaced ends of the conduit sections 8 and I4 and will strike the upper head section 'Ia approximately at its axial center, see dotted arrows in Fig. l, and at a point radially outwardly offset from the inner baie-acting end Ma of the intake duct section I4. The oil thus impinged upon the upper head member le will be spread out over the surface of said head member radially outwardly of the haine-acting inner end Ita of the conduit section I4 and will be trapped by the projecting baite-acting portion Ita against the passage into the conduit section It for the brief duration o the back surge pressure resulting from the backfire explosion. When thisy instantaneous back pressure has subsided, such oil as is trapped within they chamber i3 will readily drain back through the intake section 8 to the oil well.

The above described backfire trap has proven highly efficient in extensive commercial use under a wide variety of conditions, reduces toy a very minimum the restriction to normal air flow set up by such devices, cannot become plugged, up in operation, and can be provided at a very mini- `mum cost over and above the cost' of the air cleaner proper.

What 1 claim is:

In an air cleaner for an engine intake manifold including a casing having an oil reservoir, an air inlet conduit extending generally vconcentrically through said casing to said reservoir, and an air outlet leading from said reservoir, said inn let conduit comprising vertically spaced laterally offset sections and an intermediate unobstructed expansion chamber of materially greater diameter than said sections coneentrically disposed within said casing and having upper and lower opp-ositely concaved walls, said conduit sections being of substantially uniform diameter with the outer section projecting a substantial distance throughl the upper curved wall of said chamber adjacent the periphery thereof and providing an oil intercepting skirt, said inner section depending coaxially from said chamber and out of register with said outer section, and the eoncaved lower wall of said chamber connecting said sections and forming a substantially unbroken continuation of one side wall of each section whereby anunobstructed gently curving inlet passage way is formed through said chamber providing the minimum ofy restriction to air flow in the intake during normal operation of the cleaner, said intercepting` skirtr obstructing back-flow of oil in the, event, of backfire.

FRANK A. DONALDSON. 

